[tip:perf/core] tools include: Add a __fallthrough statement

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  b5bf1733d6a391c4e90ea8f8468d83023be74a2a
Gitweb:     http://git.kernel.org/tip/b5bf1733d6a391c4e90ea8f8468d83023be74a2a
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Wed, 8 Feb 2017 17:01:46 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 8 Feb 2017 17:30:58 -0300

tools include: Add a __fallthrough statement

For cases where implicit fall through case labels are intended,
to let us inform that to gcc >= 7:

    CC       /tmp/build/perf/util/string.o
  util/string.c: In function 'perf_atoll':
  util/string.c:22:7: error: this statement may fall through [-Werror=implicit-fallthrough=]
      if (*p)
         ^
  util/string.c:24:3: note: here
     case '\0':
     ^~~~

So we introduce:

  #define __fallthrough __attribute__ ((fallthrough))

And use it in such cases.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: William Cohen <wcohen@redhat.com>
Link: http://lkml.kernel.org/n/tip-qnpig0xfop4hwv6k4mv1wts5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/include/linux/compiler.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index e33fc1d..d94179f 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -126,4 +126,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 #define WRITE_ONCE(x, val) \
 	({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 
+
+#ifndef __fallthrough
+# if defined(__GNUC__) && __GNUC__ >= 7
+#  define __fallthrough __attribute__ ((fallthrough))
+# else
+#  define __fallthrough
+# endif
+#endif
+
 #endif /* _TOOLS_LINUX_COMPILER_H */